In an absorbance detector used for a liquid chromatograph or the like, a container that is referred to as cell is irradiated with light for measurement from a light source in such a state that the container is filled in with a liquid to be measured (hereinafter referred to as sample liquid) or the liquid continuously flows through the container so that the intensity of light that has transmitted through the sample liquid is detected, and thus, the absorbance for each wavelength thereof is found. In order to measure a microscopic amount of sample liquid with a high level of sensitivity, it is necessary for the cross-section of the cell to be small and for the length of the optical path to be long. Therefore, a conventional cell that is referred to as light guide cell or the like has been put into practice, where a linear capillary is used as the cell in such a manner that light enters through one end side of the capillary in the direction in which the capillary extends so as to be totally reflected from the outer or inner wall of the capillary and transmitted to the other end side of the capillary (see Non-Patent Document 1 and Patent Documents 1 to 3).
As a flow cell for allowing light to be totally reflected from the outer wall of the capillary and be transmitted, a flow cell where fused quartz is used for the capillary so that light is totally reflected from the interface between the quartz of the outer wall and air has been known (see Patent Document 1).
As a flow cell for allowing light to be totally reflected from the inner wall of the capillary and be transmitted, a flow cell where the capillary of which the inner wall is coated with Teflon (registered trademark) AF has been known (see Patent Document 2).
Light waveguides, such as optical fibers, are often used to allow light for measurement to be emitted from the light source and enter into the capillary.